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Climate Change Impacts on Water Resources in Colorado <br /> Report for the Colorado Water Conservation Board <br /> Prospectus <br /> The Colorado Water Conservation Board has commissioned the NOAA -CU Western <br /> Water Assessment to prepare a report on the state of the science of the observations and <br /> projections of the physical impacts of climate change in order to understand their effects <br /> on water resources in the state of Colorado. This document will be aimed at planners, <br /> decisionmakers, and policymakers in water in Colorado. It will explore and describe how <br /> climate change may affect Colorado's water through its snowpack, runoff, temperature, <br /> and evapotransporation. The report is also intended to complement and provide the <br /> background for a related report proposed by the Rocky Mountain Climate Organization — <br /> this report focuses primarily on the physical aspects of the system that are relevant for <br /> water resources (temperature, precipitation, snowpack, timing of snowmelt, extreme <br /> events, etc), and leaves the assessment of sensitivities and vulnerabilities of water supply <br /> to the later report. <br /> In the recent IPCC Fourth Assessment Report (2007), 22 global climate models <br /> developed at 16 climate modeling centers were used to project changes in temperature <br /> and precipitation to the year 2100 and beyond. These models agree that global average <br /> temperature will increase, and agree in general that the global hydrologic cycle will <br /> become more intense. Climate projections for Colorado have been developed by <br /> downscaling these global climate models using bias - corrections and local climate <br /> information to represent features that are not present in the global simulations. Although <br /> there is more uncertainty in the regional projections, than the global ones, initial findings <br /> for the state of Colorado include: <br /> • Annual temperature is likely to increase in the range of 3.6 °- 12.6 °F by 2100. <br /> Summertime temperatures may increase more than wintertime temperatures, <br /> though it is difficult to quantify by how much in the current assessment. <br /> • There is much less agreement among the climate models about changes in annual <br /> precipitation over Colorado. <br /> • Climate models (on average) are projecting an increase of 0.4 inches of <br /> precipitation in the winter (Dec -Mar), and a decrease of up to 0.4 inches in the <br /> spring (Apr -Jun). <br /> • Increased temperatures and increased evaporation in the summer would also result <br /> in increased water demands by agriculture and for other uses such as lawn <br /> watering. <br /> Governor's Climate Change Action Plan sets out a goal to prepare the state to adapt to <br /> those climate changes "that cannot be avoided." Actions recommended include an <br /> investigation of vulnerabilities of the state's water supplies to climate change, analysis of <br /> impacts on interstate water compacts, and planning for severe drought, flooding and other <br />